#3 Is it necessary to consider the difference in pixel area between SP1 and SP2 when generating PhotonCount data input to Sensor Model?

Not necessary.

The difference in sensor sensitivity between SP1 and SP2 is considered in the sensor model. In the rendering system, use the pixel pitch as the sensor for both SP1 and SP2 instead of the actual pixel pitch of SP1/SP2.

To get the pixel pitch [μm], specify PixelUnitUm as the argument in the GetPropertyFloat function of the generic I/F.

For details about the generic I/F, refer to the latest generic I/F specification.